Although exposed used syringe and intravenous needles have always presented a danger of transmitting infectious disease, the recent and highly publicized alarming spread of AIDS virus has focused attention on the problem. Whereas the possibility of an accidental engagement with the end of a used syringe or intravenous needle may have once been considered a minor annoyance associated with a pin prick, physicians, nurses, and other hospital and medical office personnel are now aware that their very lives are threatened by the existence of used syringe and intravenous needles which have not been properly discarded. In the course of a lawsuit recently given high notoriety, it was alleged that a physician contracted AIDS by accidentally pricking herself with a needle carelessly left among the bed sheets of an infected patient who had been injected with the needle.
The need for making a needle safe after use is well known but none of the solutions proposed to date adequately addresses the problem. In order to be effective, such a solution must be economical, that is, it must not unduly increase the cost of a syringe or intravenous needle assembly which is a high volume disposable item. Protection of the used needle must also be automatic so as to avoid compromise of safety by human error.
Proposed devices of the prior art fail to meet the foregoing criteria. For example, U.S. Pat. No. 4,790,828 to Dombrowski et al. for a Self-Capping Needle Assembly discloses a syringe with a relatively complex cap member having moving parts and projections that must be squeezed together to move the protective part of the cap member over the tip of the needle. U.S. Pat. No. 4,861,338 to Mathiesen et al. for a Safety Syringe is directed to a device for retracting the syringe needle into a sheath much like the writing cartridge of a ball point pen is retracted into the barrel of the pen. The foregoing devices of the prior art are relatively expensive and complex and their designs require the intervention of the physician, nurse or technician using the syringe or intravenous device to make the used needle safe.